A multiple access mobile communication system enables a plurality of mobile stations to establish radio communication substantially simultaneously, by haring radio resources including at least one of time, frequency, and transmission power among the plurality of mobile stations. Typical examples of multiple access schemes include TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access), CDMA (Code Division Multiple Access), OFDMA (Orthogonal Frequency Division Multiple Access), and any combination thereof.
Unless noted otherwise, the term “a mobile communication system” used in the present specification refers to a multiple access mobile communication system. A mobile communication system includes mobile stations and an upper network. An upper network includes base stations, a relay node that relays traffic, and a control node that performs radio resource management, mobility management, bearer management and the like.
When new downlink traffic (downlink data or incoming voice call) to a mobile station in a standby state has arrived at an upper network, the upper network sends a paging signal to the mobile station. The mobile station in the standby state performs a discontinuous reception (DRX) for receiving a paging signal. In response to receiving the paging signal designated thereto, the mobile station starts initiates signaling in order to perform communication for receiving the downlink traffic. This signaling includes transmission of a response message to the paging. The response message includes one or both of a request for establishing a control connection and a service request for establishing a communication path (bearer) for user data. The network receives the response message and then performs procedures for establishing the control connection and the communication path (bearer) required for sending the downlink traffic to the mobile station.
Note that, to page a mobile station, the upper network has to determine an area where a paging signal is sent. In the present specification, “an area where a paging signal is sent” is referred to as “a paging area”. A paging area includes at least one cell (or sector), and generally includes a plurality of cells (or sectors). Typically, a paging area for a mobile station is identical to the latest location registration area to which the mobile station belongs. The location registration area is a fundamental unit in the upper network for managing a location of the mobile station in the standby state. The mobile station sends a location update request to the upper network when the mobile station crosses over from one location registration area to another. Further, the mobile station may periodically send a location update request irrespective of occurrence of any change in the location registration area.
For example, in connection with the packet exchanged domain of the UMTS (Universal Mobile Telecommunications System) of the 3GPP (the 3rd Generation Partnership Project), the location registration area is referred to as a routing area (RA). Accordingly, paging of a mobile station in a standby state (CELL_PCH state or URA_PCH state) is generally performed by broadcasting a paging signal over the entire routing area.
Further, in the LTE (Long Term Evolution) of the 3GPP, the location registration area is referred to as a tracking area (TA). Accordingly, paging of a mobile station in a standby state (RRC_IDLE (ECM_IDLE) state) is generally performed by broadcasting a paging signal over the entire routing area.
Patent Literatures 1 and 2 disclose the technique of determining narrower paging area as compared to the normal location registration area through use of a movement history of a mobile station. By narrowing the paging area, the paging load on the mobile communication system can be reduced.
Patent Literature 1 discloses calculating a movement distance per unit time (i.e., a moving speed) of a mobile station using a history of location update requests sent from the mobile station, and determining, as the paging area, base stations within a circle having a radius equal to the calculated movement distance.
Patent Literature 2 discloses performing a location management of a mobile station using not only the location update requests but also GPS (Global Positioning System) location information. The method disclosed in Patent Literature 2 includes determining, when the latest location information of a mobile station obtained by the upper network is GPS location information, reduced paging area which is narrower than the location registration area based on the GPS location.
Further, Patent Literature 2 discloses calculating a moving speed of a mobile station using a history of location update messages and that of GPS location information, and increasing the paging area as the moving speed of the mobile station becomes larger. Specifically, in order to enlarge the paging area, an identifier for specifying the paging area is changed in order of a sector identifier, a radio network controller (RNC) identifier, and a routing area indicator (RAI).